vitamin
Vitamin C: How Much Per Day, Forms, Iron and Limits
Also known as ascorbic acid, L-ascorbic acid, sodium ascorbate, calcium ascorbate, Ester-C, buffered vitamin C
Short answer
Vitamin C (ascorbic acid) is a water-soluble vitamin the body cannot make. It uses it to make collagen and as an antioxidant, and it helps absorb plant iron. Supplement ascorbic acid is absorbed as well as vitamin C in food. Absorption falls below 50% above 1 g a day. The adult upper limit is 2,000 mg a day [1].
Last reviewed · 3 sources
What is Vitamin C?
Vitamin C, also called L-ascorbic acid, is a water-soluble vitamin that humans cannot make, so it must come from food or supplements [1]. The body needs it to make collagen, L-carnitine and some neurotransmitters, and it is involved in protein metabolism [1]. It also acts as an antioxidant, plays a role in immune function, and helps the body absorb nonheme iron from plant foods [1]. The body cannot store it, so it is needed every day [2].
Forms of Vitamin C you'll see on labels
Ascorbic acid
The most common supplement form. It is absorbed as well as the vitamin C naturally in foods such as orange juice and broccoli [1].
Sodium ascorbate, calcium ascorbate and other mineral ascorbates
Other forms sold as supplements [1].
Ascorbic acid with bioflavonoids
One study found no difference in blood vitamin C levels compared with plain ascorbic acid [1].
Ester-C (calcium ascorbate blend)
One study found the same blood levels as ascorbic acid; another found no difference in blood levels or urine loss [1].
How much Vitamin C do adults need?
NIH lists these Recommended Dietary Allowances (RDA) for adults 19+, in mg. People who smoke need 35 mg a day more. Reference values, not a personal recommendation.
| Group | Amount per day |
|---|---|
| Men 19+ | 90 mg |
| Women 19+ | 75 mg |
| Pregnancy 19+ | 85 mg |
| Lactation 19+ | 120 mg |
| People who smoke | 35 mg a day more than the RDA |
Upper limit: 2,000 mg a day for adults 19+, including during pregnancy and lactation, from food and supplements. It does not apply to people receiving vitamin C as medical treatment under a doctor's care [1].
How Vitamin C appears on a label
Vitamin C is listed in mg. The Daily Value (DV) used for % DV is 90 mg for adults and children 4 and older [1]. NIH notes that about 70% to 90% is absorbed at 30 to 180 mg a day, but less than 50% at doses above 1 g (1,000 mg) a day, and the unused amount leaves in urine [1].
When to take Vitamin C
No official source names a best time of day to take vitamin C or says whether to take it with food. NHS advice for iron tablets says a doctor may suggest taking them with orange juice or vitamin C, because vitamin C helps iron absorption [3].
What to keep apart from Vitamin C
Iron
Vitamin C helps the body absorb nonheme iron, the form in plant foods [1]. A doctor or pharmacist may suggest taking iron tablets with orange juice or vitamin C [3].
Chemotherapy and radiation
Using antioxidants such as vitamin C during cancer treatment is controversial. NIH says people having chemotherapy or radiation should talk to their oncologist before taking vitamin C, especially in high doses [1].
Statins with niacin
Vitamin C with other antioxidants may blunt the HDL rise from niacin plus simvastatin [1]. Ask your pharmacist or doctor.
Foods that contain Vitamin C
- Red and green peppers
- Oranges and orange juice
- Grapefruit and grapefruit juice
- Kiwifruit
- Broccoli
- Strawberries
- Brussels sprouts
- Tomatoes and tomato juice
- Cantaloupe
- Potatoes
Who should ask a doctor or pharmacist first
Talk to a doctor first if you have hereditary hemochromatosis, since high vitamin C doses could worsen iron overload [1]. Ask too if you have kidney disease or a history of kidney stones, or high oxalate levels (hyperoxaluria) [1]. If you are having chemotherapy or radiation, ask your oncologist before taking vitamin C [1].
Keep Vitamin C in a routine that fits
Supin schedules what you take by time of day, reminds you, and tells you when a bottle runs low.
Vitamin C: questions people ask
Yes. Vitamin C is L-ascorbic acid, and the ascorbic acid in supplements is absorbed as well as the vitamin C in food [1].
Research is mixed. NIH says regular vitamin C does not appear to reduce the risk of colds in the general population, though it may modestly shorten them; taking it after symptoms start does not appear to help [1].
Yes. Vitamin C helps the body absorb nonheme iron, the form found in plant foods [1].
Heat and long storage can reduce vitamin C in food. Steaming or microwaving may lessen the loss [1].
Sources
- Vitamin C: Fact Sheet for Health Professionals — NIH Office of Dietary Supplements
- Vitamin C - Vitamins and minerals — NHS
- How and when to take ferrous sulfate — NHS
Educational information, not medical advice. The amounts above are official reference values, not a recommendation for you. Check with your doctor or pharmacist before starting or changing supplements, especially if you take medication, are pregnant or have a health condition. Supin sells a subscription, not supplements. Last reviewed .